Hi,
sorry, ccing the list since virt-tools-list is *not* setup to
automatically reply to this list if not replying to all (but some lists
do have default "Reply-To" header to the list so changing this to list
itself should be good).

IMHO, we should simply disallow that. Users would expect that
cloning a guest is guarneteed to not impact the original. If
we can't guarentee that, we should refuse to clone it. Swiching
a private disk to shared mode is giving a user a loaded gun
with no safety catch & a touch sensitive trigger.

Are you saying we should disallow sharing any private disks, or only
ones that it appears we can't clone? I suppose any shareable disks
should be marked with <shareable/> in the XML, but that currently isn't
obvious to the user, or easy via any of the tools atm. The cases when a
user would actually want to share a r/w disk though are rare enough that
we should require the sharable flag, and deny the clone operation otherwise.
- Cole

Well, I don't know whether it's appropriate or just some off topic
because this is not what's this about but I don't understand
virt-manager/python-virtinst/libvirt much yet but when I was working on
Xen (and virt-manager should support Xen) there was a duplicate check
and it was all based on uname (physical disk path) and mode. So I think
we should consider mode into that and disallow cloning (sharing) disk
images that are write-exclusive etc... But we should make there an
option to copy this one disk into another disk image (like in
vmm-clone-storage) and put this one into XML configuration per new VM
so I guess just giving the warning about sharing read/write disk is not
a good way. We should consider whether the domain is running and when I
did a duplicate check to Xen this disallows 2 concurrently running
guests use the same disk image not to cause disk corruption so this
should not be allowed so is really sharing read/write disk image a good
option? At least Xen will disallow this with error message that the
disk is already in use.

The readonly images, like mounted ISOs into VMs, should be shareable
between all the guests because there's no risk of multiple write
accesses and therefore a disk corruption of this one.

Also, cloning MAC addresses should have a check for duplicate MAC
addresses not to have MAC conflicts there.